The sudden discovery of a red or pink stain in a newborn’s diaper understandably causes worry for parents. While this observation should always prompt a call to your pediatrician for assessment, many causes are benign and temporary. Understanding the potential reasons can help parents remain calm while seeking medical guidance. The appearance may not always be true blood, and even when it is, the cause is often a minor, easily managed issue.
The Appearance of “Brick Dust”
The most frequent cause of a red or pinkish-orange discoloration mistaken for blood is “brick dust” urine. This temporary phenomenon is caused by a high concentration of urate crystals, which are crystallized uric acid, a normal waste product. These crystals are not blood, but their color can be alarming, often leaving a powdery, brick-colored stain.
Urate crystals are most common during the first few days of life, particularly in breastfed newborns while the mother’s milk supply transitions. The newborn’s kidneys concentrate urine during this period of lower fluid intake. This occurrence is harmless and typically disappears once the baby consumes larger volumes of milk and hydration improves.
Causes Related to Maternal Hormones or Swallowed Blood
In some cases, the red stain is true blood related to benign and self-limiting hormonal factors. Newborn girls may experience minor vaginal bleeding, often called pseudo-menstruation. This is a physiological response caused by the withdrawal of maternal estrogen hormones that crossed the placenta during pregnancy.
This hormonal withdrawal bleeding usually begins between two and ten days after birth, presenting as a small amount of pink or blood-tinged vaginal discharge. The episode is typically brief, lasting only two to five days, and resolves without intervention. Any bleeding lasting longer than a few days or exceeding minor spotting should be reported to the pediatrician.
Another common cause of actual blood in a newborn’s stool is the ingestion of maternal blood. This can happen during a vaginal delivery if the baby swallows blood from the birth canal. Alternatively, a nursing infant may ingest blood from the mother’s cracked or bleeding nipples.
When swallowed, the maternal blood passes through the baby’s gastrointestinal tract. It may appear in the stool as dark, tarry, or coffee-ground-like flecks, or as maroon-colored streaks. This blood is not harmful and does not require treatment. An Apt test can determine if the blood is fetal or maternal in origin.
Gastrointestinal Irritation and Allergic Reactions
When bright red blood streaks are observed on the surface of the stool, a common cause is minor trauma to the lower gastrointestinal tract, such as an anal fissure. This is a small tear in the delicate skin of the anus or the lining of the rectum. Tears typically occur when a baby passes a hard or large stool, or sometimes a very frequent, watery stool, which irritates the sensitive tissue.
The blood from a fissure is bright red because the injury is near the end of the digestive tract, indicating fresh blood. Anal fissures are the most frequent cause of blood in the stool of otherwise healthy infants and often heal quickly with basic home care. A pediatrician may recommend measures to soften the stool or use an ointment.
A more complex cause is allergic proctocolitis, often linked to a Cow’s Milk Protein Allergy (CMPA). This occurs when the baby’s immune system reacts to proteins, commonly from cow’s milk or soy, that pass into breast milk or are present in formula. The immune reaction causes inflammation in the colon and rectum lining, leading to blood and often mucus in the stool.
Allergic proctocolitis typically presents in infants who are otherwise well-appearing and gaining weight appropriately, with symptoms usually starting within the first two months of life. Treatment involves eliminating the offending protein from the baby’s diet. This requires the breastfeeding mother to remove dairy (and sometimes soy) from her diet, or switching the baby to a hypoallergenic formula. The blood may take up to four weeks to clear, as the intestinal lining needs time to heal.
Other, less common causes of blood in the stool include infections, such as bacterial gastroenteritis, which causes inflammation and bloody diarrhea. A severe diaper rash can also cause superficial bleeding from open sores. In rare instances, particularly in preterm infants, necrotizing enterocolitis (NEC) can cause bloody stool, but these infants are typically severely ill.
When to Contact Your Pediatrician Immediately
While many causes of blood in a newborn’s diaper are minor, any presence of blood warrants discussion with a healthcare provider. Specific red flags, however, require immediate medical evaluation.
Urgent attention is necessary if the baby is younger than 12 weeks old and has significant bloody stool. Immediate care should also be sought if the baby displays signs of general illness, such as fever, lethargy, or excessive sleepiness.
Signs Requiring Emergency Care
Other symptoms necessitating emergency care include projectile vomiting, a swollen or distended abdomen, or refusal to feed.
The color and consistency of the stool can also indicate an emergency. Black, tarry stools in an infant past the meconium stage signal bleeding higher up in the gastrointestinal tract and require prompt assessment.
Immediate medical attention is necessary if the bloody stool is accompanied by severe diarrhea or signs of dehydration (e.g., few wet diapers, a sunken soft spot, or dry lips).